The operation principle of a photoelectric distance sensor is that, an object is illuminated with light emitted by a light source, and light reflected by the object is received and converted into an electrical signal by a photoelectric sensing device. The photoelectric distance sensor is suitable for various daily applications. For example, the photoelectric distance sensor may be used in a mobile phone to detect talking posture of a user.
In order to meet design requirements for full-screen display devices, a light transmissive display screen is usually adopted, and the photoelectric distance sensor is arranged under the light transmissive display screen to perform distance sensing. In the conventional technology, an optical sensing system including a light transmissive display screen is shown in FIG. 1. The optical sensing system mainly includes a light emitting element 101, a light sensing element 102, and a light transmissive display screen 104. The light emitting element 101 and the light sensing element 102 are arranged on a substrate 105, and are encapsulated in an encapsulating body 106. A light emitting surface A and a light receiving surface B are provided on a surface of the encapsulating body. The light EL is emitted by the light emitting element 101 to outside of the encapsulating body 106 via the light emitting surface A and is transmitted to the light transmissive display screen 104. Then, the light transmitted to the light transmissive display screen 104 is transmitted to a to-be-detected object 103, and is reflected by the to-be-detected object 103 to form the reflecting light RL. The reflected light RL passes through the light transmissive display screen 104, and reaches the light sensing element 102 via the light receiving surface B. The light sensing element 102 receives the reflected light RL and performs distance sensing on the to-be-detected object based on the intensity of the reflected light RL.
In the above conventional optical sensing system, the volume of the encapsulating body are required to be relatively small due to the high manufacturing cost, which results in the small light emitting surface. In this case, the energy of the light emitted from the light emitting surface is mostly concentrated at a small region (as indicated by a region surrounded by dotted lines in FIG. 1) of the light transmissive display screen, easily causing light spot phenomenon on the light transmissive display screen.